1. Helminthotheca echioides (Linnaeus) Holub, Folia Geobot. Phytotax. 8: 176. 1973.
Picris echioides Linnaeus, Sp. Pl. 2: 792. 1753
Leaf blades 50–150(–250) × 10–50(–80+) mm. Peduncles 1–5+ cm, bristly hispid. Calyculi: bracts 9–15+ × 3–5+ mm, margins and tips bristly-ciliate. Phyllaries often sigmoid in fruit, abaxial faces and tips bristly. Cypselae: bodies 2.5–3 mm, beaks 2.5–5 mm; pappi 4–7 mm. 2n = 10.
Flowering May–Nov. Disturbed sites; 0–50(–500) m; introduced; Alta., N.B., Ont., Sask.; Ariz., Calif., Conn., D.C., Iowa, Maine, Md., Mass., Mo., Mont., N.J., N.Y., N.Dak., Ohio, Oreg., Pa., Vt., Va.; Europe; widely introduced elsewhere.
Reports for British Columbia and Nova Scotia need confirmation.